Cleaning systems for use in removing debris from bodies of fluid, for instance, swimming pools, often have an automatic cleaner attached through fluid carrying lines to a pump that moves fluid, in which debris is entrained, through the lines to a filtering system. Fluids pumped through such systems often exhibit variations in flow that cause spikes or pulses that may travel through and disrupt the system. It is desirable to prevent such spikes and even when their prevention is impossible, it may be necessary to mitigate their effects, which range from destroying fluid carrying lines to placing sharply variable loads upon the automatic cleaners, lines, valves or pump that together move fluid through the system. Such variable loads may decrease drastically the life of the components of the cleaning system.
One method of avoiding or mitigating the effects of pressure variations is to provide a control valve having an auxiliary path through which fluid can flow in order to balance the system. U.S. Pat. No. 1,853,863 to Hornbruch discloses a control valve for gas burners. Hornbruch teaches a valve that uses a bias means or spring to hold a piston in a position that closes a bypass inlet, which is connected to a mixing chamber, to the passage of gas. A pressure chamber underneath one end of the piston is connected via a duct to a tube through which air flows into the mixing chamber. When the pressure within the chamber overcomes the bias of the spring, the piston, which has a reduced in size portion, will move to allow gas to flow through the reduced portion and into the mixing chamber. The bias means can be set to require an initially higher or lower chamber pressure to move the piston. While suitable for use with gaseous materials, the Hornbruch valve is not useable with fluids in which debris is entrained. Such debris would quickly become trapped in the reduced portion of the piston and block the opening. Additionally, the Hornbruch valve is not responsive to sharp and rapid pressure variations. In fact, Hornbruch teaches that a piston should be used "inasmuch as the friction between it and the walls prevent rapid fluctuation or fluttering of the combustible gas control valve."
However, rapid pressure variations, such as a spike or "water hammer," occur frequently in swimming pool cleaning systems since debris may be ingested by the cleaning system and block certain portions of the system to thereby cause an undesired and disruptive pressure spike. This danger is particularly enhanced when it is desirable to provide a skimming action that ingests debris that floats on the top surface of the fluid. Debris such as leaves often has a large surface area and may therefore more readily block fluid lines, possibly preventing the cleaning system from continuing cleaning operations. Of course, this problem can be mitigated by providing a self-contained skimmer, such as the one disclosed by U.S. Pat. No. 3,767,055 to Flatland, entitled "Skimmer for a Water Body." The disclosed skimmer is propelled about a swimming pool and has a float that positions the skimmer upon the surface of the pool. An opening located opposite the propeller leads to a filter basket in which debris is trapped after it enters the opening. The skimmer may also be driven by an outlet pipe that provides a jet of water supplied by a hose leading to the pool filter return. If, however, automatic cleaning of the total swimming pool is desired, the disclosed skimmer cannot accomplish both its skimming function and cleaning of the pool bottom.
A series of U.S. Pat. Nos. 4,317,243, 4,368,751 and 4,378,254 to Chauvier each disclose "a valve by means of which a major portion of the suction flow of a swimming pool filtration system is channeled through an automatic cleaning device which cleans the floor and/or wall of a swimming pool, and a minor portion of the suction flow is drawn from the surface of the pool thereby to skim the surface." The valve assembly, which is connected between an automatic pool cleaner and a suction pump, has an auxiliary inlet adjacent the pool surface and a closure member that is capable of opening and closing the auxiliary inlet. A bellows assembly and spring engaging the closure member effectively "pre-loads" it, thereby resisting movement of the closure member that would otherwise open the auxiliary inlet. Lowering the internal pressure of the valve causes the spring to compress, moving a frame that in turn forces, or "induces," the flap to open. This inducement is accomplished by the bellows assembly, which communicates with the interior of the valve and is mechanically connected to the spring.
Under normal operating conditions, the closure member eventually reaches an equilibrium, "intermediate" position in which the auxiliary inlet is partially open. If leaves, papers, or other surface debris block the partially-open auxiliary inlet, the resulting pressure differential will displace the bellows assembly, "compressing the spring . . . and decreasing the force by means of which the flap . . . is held in its" initial, closed "position. As a result, the flap . . . will open, allowing water to be sucked into the housing . . . through the" auxiliary inlet and drawing away the debris. Such bias towards the open position when detritus blocks the auxiliary opening occurs as a result of a decrease of pressure in the chamber formed by the bellows assembly that compresses the spring and biases the closure member toward the full open position. In order to move the flap to the full open position, the spring must be compressed through a significant distance. Thus, without the bellows assembly compressing the spring in response to decreased fluid flow through the valve, the closure member cannot open to ingest the debris and the auxiliary inlet will therefore be blocked.
Chauvier accordingly teaches that decreasing the bias force holding the closure member closed is essential to operation of the valve. Moreover, in the Chauvier valve, variation in the bias force that forces the flap closed must track directly the varying fluid flow through the auxiliary inlet; as fluid flow through the auxiliary inlet increases, bias force increases and the closure member closes, and, as fluid flow through the auxiliary inlet decreases, bias force decreases and the closure member opens. This variation in bias force in response to blockage of the auxiliary inlet is critical because, according to Chauvier, there are "systems in which an aperture in a cover is closed by means of a disc, the disc being biased against the cover by means of a spring. With such systems, the biasing force is independent of the amount of water flowing through the aperture and, in use, the restricted passage provided between the cover and the disc becomes blocked with leaves and the like."
In the Chauvier valve, "the main flow of water will be through the cleaning device, with a lesser amount of water flowing through the restricted aperture of the auxiliary opening." Accordingly, a major disadvantage of using the Chauvier valve, with its almost exclusive focus on skimming the surface of the water, is that it may not provide a sufficient fluid flow through the auxiliary inlet to the cleaning system to balance large pressure variations while maintaining a nearly constant flow through the automatic swimming pool cleaner. Nor can the Chauvier valve operate with the various automatic swimming pool cleaners that may each operate at a different optimal flow rate. For instance, in one system it may be desirable to provide a 14 gallons per minute (gpm) fairly constant fluid flow rate to the cleaner. For other systems, a relatively higher constant fluid flow rate may be necessary. It is therefore often necessary to adjust the threshold at which the auxiliary path in a valve opens in order to allow use of the valve with various systems. However, the only way in which the Chauvier valve could be so adjusted would be to replace completely the bellows assembly or disassemble the bellows assembly in order to exchange the spring within the bellows assembly for a stronger or weaker spring. Such a process is at the least time consuming and difficult.
Notwithstanding Chauvier's teaching to the contrary, it is possible and desirable to provide a flow control valve that skims the surface of the body of fluid in which it operates and covers a bypass inlet in such a way that the opening and closing of the cover is independent of the amount of water flowing through the bypass inlet and may be accomplished without the complex, unwieldy bellows assembly structure that is central to the Chauvier valve. Instead, it is desirable for the flow control valve to be responsive to the rapid pressure changes within the system rather than merely blockage of the skimmer aperture, and for the valve to be capable of ingesting large amounts of bypass fluid through a bypass inlet to compensate for large pressure variations within a variety of automatic cleaning systems.